Field of the Invention
The invention relates to a comb filter containing series connected integrators, to which is fed a digital data stream at a high sampling rate in order to yield a digital data stream at a low sampling rate.
So called decimation filters are used to convert a digital data stream having a high sampling rate into a data stream having a low sampling rate. The filter function of such decimation filters usually has low pass filter properties and effects an increase in the word width of the data decimated by the decimation filter. A 1 bit stream at a high sampling rate can thus be decimated into, for example, 16 bit words in the voice band.
One field of application is digital telephony. In this case, at least one such decimation filter is connected downstream of a Sigma Delta analog/digital converter.
The decimation factor of a decimation filter is usually determined by a power of two, that is to say 2, 4, 16, 64, etc. The usual structure for such a decimation filter is afforded by a comb filter, since a filter of the latter type can be realized with a relatively low outlay.